My advice.
1) Fit a magnetic cleaner to the system (reasonably easy to do and not that expensive).
2) Add a decent system cleaner, run for a week or so.
3) Drain and flush system, either each individual radiator or you can modify your system with a few t-pieces and isolating valves so you can blast cold water through it.....just like a power flush and just as effective.
The magnetic cleaners work very very well though and given they are easy to fit and about 60-70 quid, a very worth while addition.
This isn't my house.....my house, the heating works well, new boiler a few years ago and had to have a 'MAGNA Clean' or similar fitted for the boiler warranty

Very little sludge is cleaned out of it every boiler service, but was power flushed before new boiler was fitted.
Its my mums bungalow......one rad doesn't work at all (doesn't have air in it or a stuck TRV, ive checked) other rads heat up at different temps, plus the boiler imo shuts down too quickly and for too long, so the rads that do work (but don't get anywhere as hot as they should) go cold before the boiler fires back up again. To me indicating a system that is sludged up and the water isn't flowing properly (pump is humming away, so that seems to be working)
Spoke to another plumber today, that lives in the village my mum does.....
He's going to visit on Thursday morning, but he's in the middle of another job at the moment and is booked up until the first week of Feb. But he said he can spare an hour Thurs.
His plan of action on thurs is....
Disconnect each rad to see what comes out
Only run one rad at a time to see what sludge is left can get moving again...
Then first week of Feb....fit a magnetic cleaner to get the rest of the sludge out ...
He might have other ideas like Mark suggested ....ie a cleaner in the system for a week or two....before mag cleaner is fitted.
No mention of a power flush from him.........
These are all jobs I could do......but as my mum isn't a 'poor' pensioner and having had 3 weeks off with a bad cold (back at work this week) she can afford a plumber to sort it for her......just been trying to find one that will do a decent job for a fair price

Think I may have found one ....we shall see ....
Thanks for the advice
